GENETIC DIVERGENCE BASED ON METRIC AND PHYSIOLOGICAL TRAITS IN UPLAND COTTON (Gossypium hirsutum L.)
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Date
2011
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ACHARYA N. G. RANGA AGRICULTURAL UNIVERSITY
Abstract
The present investigation was carried out during kharif 2009-10 at Regional
Agricultural Research Station, Lam farm, Guntur with 70 genotypes of cotton
(Gossypium hirsutum L.) to know the extent of genetic variability, heritability,
genetic advance as per cent of mean, character association, the magnitude of direct
and indirect effects of yield component traits on seed cotton yield and genetic
divergence based on 19 characters viz., number of sympodia per plant, number of
bolls per plant, boll weight (g), seed index (g), lint index (g), ginning out-turn (%),
2.5% span length (mm), micronaire (10 -6g/in), bundle strength (g/tex), uniformity
ratio, fibre elongation (%), crop growth rate at 60-120 days (g/m2/day), relative water
content at 60 DAS (%), relative water content at 120 DAS (%), specific leaf weight at
60 DAS (mg/cm2), specific leaf weight at 120 DAS (mg/cm2), leaf area index at 120
DAS, harvest index and seed cotton yield per plant (g).
The genotypic coefficient of variation for all the characters studied was lesser than
the phenotypic coefficient of variation indicating different levels of interaction of
each character with environment. High variability was recorded for number of
bolls per plant, crop growth rate at 60-120 days and leaf area index at 120 DAS.
High heritability and high genetic advance as per cent of mean was observed for
the characters viz., number of bolls per plant, boll weight, seed index, lint index,
2.5% span length, micronaire, CGR at 60-120 days, LAI at 120 DAS and seed
cotton yield per plant indicating the predominance of additive gene action and
hence, direct phenotypic selection may be useful with respect to these traits.
Correlation studies indicated significant positive association of number of
bolls per plant, boll weight, seed index, lint index, CGR at 60-120 days and harvest
index with seed cotton yield per plant.
The path coefficient analysis revealed that number of bolls per plant and boll
weight exerted direct positive effect on seed cotton yield per plant. Selection based
on these attributes may be helpful in evolving high yielding varieties of upland
cotton.
The results of multivariate analysis indicated presence of considerable
divergence among seventy genotypes studied which were grouped into nine
clusters in case of D2 analysis and in Ward’s minimum variance method.
Clustering pattern suggested that geographical distance may not be the only factor
causing genetic divergence among genotypes studied.
By Mahalanobis’ D2 analysis, it was noted that boll weight, CGR at 60-120 days
and ginning out-turn contributed maximum towards divergence. Based on inter-
cluster distance among the groups, it is suggested to make crosses between the
genotypes of cluster VII (AK 32) and cluster VIII (L 387) or between genotypes
falling under cluster VII (AK 32) and cluster IX (HLS 329) for generating
desirable segregants.
In principal component method, first 7 principal components explained
75.365% of the variability. The significant factors loaded in PC1 towards maximum
divergence were number of bolls per plant, lint index, micronaire, boll weight, CGR
at 60-120 days, seed cotton yield per plant and SLW at 60 DAS. 2D and 3D graphs
showed wide divergence between L 741, AET 5, CCH-05-2, CSH-01, CNO-12 and
HLS 329signifying their usefulness in cotton breeding to develop high heterotic
combinations.
Agglomerative cluster analysis revealed wide genetic distance between cluster III
(HLS 272, HLS72, MCU 11, CCH 18, CSH-01, K 3902) and VII (4085, L 606,
B4 Empire, SA 1104,JK 344, ARB 8901, AC 88, CNH 7-94-3, AET 5, CPD 431,
CPD 420, DS 28, NA 1678, BWR 39, HLS 329). Therefore, selection of parents
from these clusters for hybridization may help in developing heterotic hybrid
combinations.
The genotypes HLS 329, HLS 272, AET 5 and CSH-01 showed maximum inter-
cluster distance in all the three divergence methods. So they can be exploited for
the development of heterotic hybrids in the future breeding programmes.
Description
Keywords
cotton, genotypes, planting, sowing, genetics, yields, phenotypes, biological phenomena, gossypium hirsutum, irrigation, GENETIC DIVERGENCE, COTTON, Gossypium hirsutum L.